There is beauty in all places. Graveyards are no exception.
Graveyard nymphs are fey creatures, not undead. Their flesh is warm and alive, but it is invisible. Their bones, however, are not. And so, they often are mistaken for skeletons. Some of them wear clothes to prevent this--possibly just a sundress and a wide-brim hat. Something fashionable.
They enjoy peace and gentle repose. They find corpses calming. They find the living annoying, unless the people are quiet and do not make any sudden movements. The undead are somewhere in between.
By our standards, they are exceptionally morbid and architecture obsessed. They are voluble on the subjects of injury, infection, death, the stages of decomposition, statuary, stone engraving, crypt foundation, ossuary decoration, funeral rites, and the most attractive species of moss. They even discuss their own death and decomposition candidly, and--some say--with a certain excited breathlessness.
"It's beautiful," she'll say. "The transformation. The return to the earth. You only think differently because you associate death with pain, suffering, and loss. But death doesn't want to be those things."
"They say birth is beautiful. How is this different?"
They bond with a graveyard. They learn the names and personalities of every person buried there, and speak with them often. A graveyard becomes a social event where the nymph is the popularity queen. Even the irascible undead fall under her charm.
Nymphs like mindless undead better when they are "put to bed", and will often lead mindless skeletons and zombies back to their graves and crypts. (It's not uncommon to see a nymph leading a zombie back to it's crypt while a pair of ghouls in mossy tuxedos follow along with shovels.
Nymphs enjoy ghouls for their ability to hold a conversation. (And occasionally for their wit. Many ghouls have a great sense of dry humor.) But ghouls are also eaters of the dead, and if the ghoul cannot control their appetite, they are likely to find themselves entombed without parole.
Necromancers despise them, and go to great trouble to eradicate them.
Nymphs are bound to their graveyard; they cannot leave. They care about two things: (a) the "health" of their graveyard, and (b) being entertained. They crave attention, stories, and affection. Stimulation, in any form.
They are not evil (but nor are they godly), and most will be honest about their intentions. They will usually trade large favors if someone agrees to stay with her for a year and a day. (They usually desire the most interesting person, or the one with the most attractive bone structure.) And of course, once a nymph has bonded with you, you are bound to the same cemetery as she is. At least, until she releases you, or dies.
Nymphs have no qualms about teaching their magic to their companions. Someone who spends a year with a nymph can make an Int check for each of the nymph's spells; success indicates that they've learned the spell. (Depending on the system and the DM, even non-spellcasters might gain some magic ability.) They'll walk away with the spells engraved on bones (instead of a spellbook).
And at the end of the year, most nymphs (4-in-6) will keep their promise to release you.
HD 5 Defense leather Claw 1d6
Move human Int 12 Morale 4
+Blinding Beauty - Those who gaze upon the nymph must save or be struck permanently blind. (This usually requires see invisible, since the nymph is invisible except for the bones.)
+Druid Spells (at-will, cannot cast same spell on subsequent turn) - entomb, exhume, speak with dead, charm undead (range: touch)
The average graveyard nymph is accompanied by 2d4 undead (equal chance of zombies, skeletons, or ghouls), half of which will be unobtrusively buried nearby where they can be exhumed. The average graveyard nymph will also be able to call for help as a free action, which will bring 1d8-1 additional protectors.
A nymph who feels threatened will call for help (a free action) and then entomb herself, only exhuming herself when she can no longer hold her breath. If there is a crypt below, this can become a more versatile method of escape.
The nymph's only threatening ability is entomb. Hopefully this forces players to jump from tombstone to tombstone and scamper along rain-slick crypt roofs.
Level 2 Druid
Range 50'. A creature standing on loose dirt must save or be pulled halfway underground (usually up to their waist). If they fail this first save, they must make another save or be buried 1 foot underground per caster level. This spell is especially effective against the undead (-4 to save), but is less effective outside of a graveyard (+4 to save).
Creatures buried up to their waist require a successful Str check to free themselves (they can attempt this, or someone else can). A creature who is buried underground requires two Strength checks for every foot underground, and they cannot make these attempts (they are helpless). Digging with your bare hands is difficult (-4 to Str check).
Level 1 Druid
Range 50'. An object (buried no deeper than 5' per caster level) in soil or sand is brought to the surface. The caster must have some idea that there is something down there.
Ring of False Rot
When worn, the wearer rots away until they resemble a zombie. This effect is merely superficial, but it is not an illusion. When the ring is removed, the changes are undone. This is sufficient to fool undead into thinking you are undead, as long as you behave appropriately (i.e. like a zombie).
Potion of the Zombie
When poured into the mouth of a fresh corpse, it rises as an obedient zombie. The zombie slowly decays, and it's max HP is reduced by 1 for every day since its death.
Dust of Flesh
If thrown on a person, it heals as a potion of cure light wounds. If thrown on a mundane corpse, the corpse immediately grows flesh, and is restored as if it died mere moments ago. If thrown on a corporeal undead, the undead must save or be returned to whatever fleshy creature it was before it died, losing all undead-specific powers for the duration (1d6 rounds). (Extremely useful against wights.)